Circuit means for coupling an x-ray device to a control supply apparatus



28, 1954 J. FRANSEN ETAL 3,119,931

CIRCUIT MEANS FOR COUPLING AN X-RAY DEVICE TO A CONTROL SUPPLY APPARATUS Filed May 15, 1961 n control 7 gw gxray apparatus multlplexer tube II I FIG.1

INVENTORS JACOBUS FRANSEN GERARDUS A. BUSSING ,zwe. 2.

AG ENT United States Patent 3,119,931 CIRCUIT MEANS FGR COUPLING AN X-RAY DEVICE TO A CONTRQL SUPPLY APPARATUS Jacobns Fransen and Gerardus Adrianns Bnssing, both of Emmasingel, Eindhoven, Netherlands, assignors to North American Philips Company, Inc, New York, N.Y., a corporation of Delaware Filed May 15, 1961, Ser. No. 109,911 Claims priority, application Netherlands June 28, 1960 4 Claims. (Cl. 25093) The invention relates to coupling means for X-ray devices and more particularly to a circuit means for simplifying the connection of the control-electrode of an X- ray tube to the control supply apparatus of such devices.

It is generally the practice in X-ray devices to have the associated control supply apparatus and X-ray tube disposed at two separated locations or sites for the purpose, inter alia, of isolating the operator from the radiation produced in the vicinity of the tube and, thereby, mitigate the possibility of over-exposure to the radiation and/ or its harmful effects.

It is known in some of the X-ray devices of the prior art to provide a control-electrode to control the electron flow in the X-ray tube and to interrupt it, if necessary, without changing the filament current or the anode voltage, by supplying to the control-electrode a direct volt age of such a polarity that an electric field is produced in the proximity of the cathode which is substantially op posite the field accelerating the electrons and produced by the electric voltage of the anode.

In these known prior art devices having circuit arrangements for controlling an X-ray tube, the controlelectrode is connected to a source of control-voltage of the control supply apparatus by a separate supply conductor so that the number of current conductors connecting the cathode side of the X-ray tube to the supply apparatus is increased by one as compared with a device comprising an X-ray tube without a control-electrode. This increase requires particular measures to be taken in supplying the control-voltage to the X-ray tube, and usually comprise connecting the tube to the supply apparatus by insulated high voltage cables.

In one such type of X-ray device of the prior art utilizing an X-ray tube having two foci, a high-voltage cable having three current conductors connects the cathode side of the tube to the supply apparatus, two conductors being connected to the two filament wires associated with the cathode of the X-ray tube, and the third conductor being connected to the control grid. Experiments have shown that the interruption of the electron flow in an X-ray tube can be accomplished with an anode voltage between 100 to 150 kilovolts (kv.), and a negative control-electrode voltage of 2000 to 3000 volts with respect to the cathode. However, in order to withstand these voltages, the insulating resistance between the current conductors in the high-voltage cable must have an insulation value exceeding the conventional one and with the type of conductors in the cable available in the current state of art, the connection of an X-ray tube with a control-electrode to the supply apparatus at these voltages is hardly feasible.

An object of this invention is to provide an X-ray device having a simplified circuit means for connecting the control electrode of an associated X-ray tube to the associated control supply apparatus.

Another object of this invention is to provide an X-ray device having a simplified circuit connection means in which the respective control signals from the associate control supply apparatus are multiplexed to the respective control electrode and filament cathode of the associated X-ray tube on a frequency division basis.

Other objects of this invention include the provision of 3,ll9,931 Patented Jan. 28, 1964 an X-ray device as above which obviates the disadvantages of the prior art devices.

Accordingly, this invention features an X-ray device in which the X-ray tube and a source of alternating signals, with two relatively different frequencies, are disposed at diiferent locations or sites. These different frequency alternating signals are utilized to control, respectively, the control electrode and the filament cathode of the X-ray tube which is connected to the source by provision of a frequency division multiplexing circuit connection means.

In practicing the teachings of this invention, according to one circuit thereof, a high frequency voltage for the control electrode is derived from the filament current circuit by means of, for example, a high-frequency transformer coupling. To this end, circuit embodiments are available, which are constructed in the form of a parallel resonant circuit or of a series resonant circuit. In arrangements of the first-mentioned kind, a capacitor is connected in parallel with a high-frequency transformers primary winding, the latter being connected to the filament current circuit. While such an arrangement operates satisfactorily for many applications, the current, when passing through the winding, may give rise to an undesired heating of the transformer which may not be tolerable in some types of applications. With a series resonant circuit arrangement, however, the primary winding of the high-frequency transformer is separated from the filament current circuit by a capacitor, and thereby mitigates the undesired heating and/ or the untolerable effects thereof. In the past, use has been made of a control-electrode which is connected to a resonant circuit to obtain rapidly succeeding, transient X-ray pulses. However, in these cases, the resonant circuit is in turn coupled to the anode circuit of the tube, and is not to be confused with the aforedescribed circuit embodiments of this invention.

The above-mentioned and other features and objects of this invention will become more apparent by reference to the following description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a schematic diagram in block form of the circuit of this invention;

FIG. 2 is a schematic diagram in partial block form of an embodiment of the circuit of FIG. 1;

FIG. 3 is a schematic diagram of the frequency response means utilized in the circuit embodiment of FIG. 2; and

FIG. 4 is a schematic diagram of another embodiment of a frequency response means utilized in the circuit embodiment of FIG. 2.

Referring to FIG. 1, an X ray device has its associated X-ray tube 1 disposed at a given location or site, genenally indicated by the reference numeral I. The control apparatus 2 associated with the X-ray device is disposed at a second location II. A circuit connection means 3, disposed between locations I and 11, couples the tube 1 to apparatus 2 and provides, inter alia, for the multiplexing of certain control signals to predetermined electrodes of the tube 1 on a frequency division basis.

Referring to FIG. 2, there is illustrated an embodiment of the circuit of FIG. 1. It is to be understood, however, that the circuit of FIG. 2 is by Way of example only and that other embodiments and/or modifications may be practiced by those skilled in the art without departing from the scope of the instant invention. Thus, X-ray tube 1 is illustrated therein as comprising three electrodes, to wit, a control electrode 4 which is associated with the (anode 5 and filament cathode 6. The control apparatus, associated with the X-ray device is partially shown as comprising a source 7 of alternating signals having two relatively different frequencies adapted for the control of the control electrode 4 and filament cathode 6, the source 7 being illustrated in FIG. 2 by the broken outline and the details of which will be described hereinafter. Circuit connection means, partially shown, comprises a pair of conductors 8, 9 which are housed, for example, in the insulation envelope 10, which may comprise, for example, several rubber layers of a high voltage cable that provide a multiplex path for the transmission of the signals of source 7, which is coupled tothe inputs of conductors 8, 9, .to the control electrode 4 and filament cathode 6 of tube 1-. Anode is coupled to a suitable voltage source, not shown, of the control apparatus via conductor 11, which is accommodated in the envelope 12 of a high volt agecable, in a manner well known to those skilled in the art. At the site or location of the tube 1, respective frequency responsive means 13 and 14, illustrated in FIG. 2 in block forms, respectively, are coupled to the output of the conductors 8, 9, and each of which has a different pass band which includes, exclusively, a predetermined one of the two aforesaid frequencies. In this manner, in response to the two alternating frequency signals from source 7, the frequency response means 13, 14 provide out-put signals for the exclusive control of the filament cathode 6 and control electrode 4, respectively, of tube 1.

Referring to FIGS. 3 and 4, there, is shown, by way of example only, the, details of various embodiments of the frequency responsive means 13', 14 utilized in the circuit of FIG. 2. Accordingly, the frequency responsive means 14, FIG. 3, or 14, FIG. 4, comprises a primary winding 15' of transformer 15 connected in series, FIG. 3, or parallel, FIG. 4, with a capacitor 16, FIG. 3, or 16', FIG. 4, to form, respectively, a series, FIG. 3, or parallel, FIG. 4, resonant circuit, which is shunted acrossthe conductors 8, 9. The resonant circuit, FIG. 3 or 4, is tuned to a frequency pass band. which exclusively passes the frequency signal from source 7 adapted to control electrode 4 and is. applied between the cathode 6 and electrode 4. A signal of sufficient amplitude to adequately control the electrode 4 is obtained by selection of a transformer 15 with a suitable ratio of transformation. In the case where the signal utilized to control the electrode 4 is chosen to be a relatively high frequency signal substantially higher than the frequency of the signal used to control the fila ment cathode 6, frequency responsive means 13 comprises. av low pass filter which may consist of a capacitor 21 connected in parallel with conductors 8, 9 and a choke coil. 23v connected in series with conductor 9. This latter circuit substantially blocks any high frequency signals destined for control electrode 4 from appearing. at the filament cathode 6, while at the same time passing substantially all of the low frequency signals directed to the cathode.

Iucases where a unidirectional output signal is desired, a rectifier means comprising, for example, a diode 18.and capacitor 19may be included in the frequency responsive means. 14 or 14.

If, in addition, it is desired to operate the tube 1 by interrupting the cathode-anode current of tube 1 rapidly, a resistor may be connected in parallel with the capacitor 19, to provide a charging and discharging circuit whose RC time constant determines the rate at which the capacitor is charged and discharged and thus governs the action of the tube 1. For example, in a particular arrangement, if it is desired to operate the tube 1 for a duration of 1 n-seconds, an RC time constant of l0 seconds is required.

Means for the generation of signals of two different frequencies are well known in the art. Thus, the source 7 is illustrated in FIG. 2 by way of example only as comprising a transformer 24 whose primary winding 25 is coupled to input terminals 26 which are adapted for coupling, for example, to the supply mains of a suitable alternating current voltage generator, not shown, of a given frequency which will be utilized to control the filamentcathode 6 of tube 1, via the latters coupling through the various circuits illustrated therein to the secondary winding 27 of transformer 24.

A frequency signal generator 28, illustrated in block form and examples of which are well known in the art, has its input coupled to the terminals 26 and produces an output signal having a relatively different frequency from the aforementioned given frequency which is sup plied to the conductors 8, 9 by means of the transformer 29. The output of each of the transformers 24, 29 are provided with suitable filter means which prevent the signal with the other frequency from being coupled or fed back through its windings, and comprise, respectively, for example, the tuned circuit capacitor 30 and inductor 31, and the tuned circuit comprising capacitor 32 and the inductance of the windings of transformer 29.

Since the structural elements of the frequency responsive means aforedescribcd are usually of fairly. small dimensions, the circuit of this invention finds particular application in X-ray devices of the type in which the X-ray tube is immersed in a suitable liquid cooling medium, as for example, oil and the like. Thus, as shown in FIG. 2, the tube 1 and frequency response means, 13 and 14 are disposed in a container 33, illustrated in fragmentary sectional view, which contains a suitable cooling medium, 34, partly shown, such as oil, provided with a high resistance insulation characteristic.

In the preferred operation of the invention the frequency of the signal utilized to control the electrode 4 is chosen to be a high frequency signal and is substantialiy higher than the frequency of the signal utilized to control the filament cathode 6 which is chosen to be a low one. In this manner, the control electrode signal may be transmitted over the conductors 8, 9 at a high frequency and a low amplitude, whereas the filament cathode signal may be transmitted at a low frequency and a normal high amplitude. As is obvious to one skilled in the art, circuit elements having compatible characteristics are accordingly provided in the preferred operation as, for example, the provision of an insulated high-voltage high frequency transformer for transformer 15, etc.

While we have described above principles of our invention in connection with specific apparatus, it is to be clearly understood that this description is made only by way of example and not as a limitation to the scope of our invention as set forth in the objects thereof and in the accompanying claims.

We claim:

1. An X-ray device comprising an. X-ray tube disposed at a first predetermined location and including a filament cathode and a control electrode, a source of two control signals having relatively different first and second frequencies, respectively, disposed at a second predetermined location, said first and second frequency signals being adapted for the control, respectively, of said control electrode and said cathode, circuit connection means to couple said source to said control electrode and said filament cathode comprising a pair of conductors having an input means coupled to said source and output means, first and second frequency responsive means disposed at said first location and coupled to said output means, said first frequency responsive means being responsive to a signal of said source having said first frequency to provide a first output signal to control said control electrode, and said second frequency responsive means being responsive to a signal of said source having said second frequency to provide a second output signal to control said filament cathode.

2. An X-ray device according to claim 1 wherein said first frequency responsive means further comprises rectifier means to provide said first output signal with a given polarity.

3. An X-ray device comprising an X-ray tube disposed at a first predetermined location and including a filament cathode and a control electrode, a source of two control signals having relatively different first and second frequencies, respectively, disposed at a second predetermined location, said first and second frequency signals being adapted for the control, respectively, of said control electrode and said cathode, said first frequency signal comprising a low-voltage high-frequency signal and said second frequency signal comprising a high-voltage lowfrequency signal, circuit connection means to couple said source to said control electrode and said filament cathode comprising a pair of conductors having an input means coupled to said source and output means, first and second frequency responsive means disposed at said first location and coupled to said output means, said first frequency responsive means being responsive to a signal of said source having said first frequency to provide a first output signal to control said control electrode, and said second frequency responsive means being responsive to a signal of said source having said second frequency to provide a second output signal to control said filament cathode, said first frequency responsive means comprising a highvoltage high-frequency transformer having a primary Winding connected between said pair of conductors and having a secondary winding, a first capacitor connected in parallel With said primary winding, and rectifier means serially connected to said secondary Winding means, said rectifier means comprising a series connected diode and second capacitor, said second capacitor being further connected to said control electrode and said filament cathode to provide a control electrode output signal responsive to the electrical charge thereon.

4. An X-ray device comprising an X-ray tube disposed at a first predetermined location and including a filament cathode and a control electrode, a source of two control signals having relatively different first and second frequencies, respectively, disposed at a second predetermined location, said first and second frequency signals being adapted for the control, respectively, of said control electrode and said cathode, said first frequency signal comprising a low-voltage high-frequency signal and said second frequency signal comprising a high-voitage low-frequency signal, circuit connection means to couple said source to said control electrode and said filament cathode comprising a pair of conductors having an input means coupied to said source and output means, first and second frequency responsive means disposed at said first location and coupled to said output means, said first frequency responsive means being responsive to a signal of said source having said first frequency to provide a first output signal to control said control electrode, and said second frequency responsive means being responsive to a signal of said source having said second frequency to provide a second output signal to control said filament cathode, said first frequency responsive means comprising a high-voltage high frequency transformer having a primary Winding connected in parallel with said pair of conductors and a secondary winding, a first capacitor connected in series with said primary winding, and rectifier means serially connected to said secondary Winding means, said rectifier means comprising a series connected diode and second capacitor, said second capacitor being further connected to said control electrode and said filament cathode to provide a control electrode output signal responsive to the electrical charge thereon.

References Cited in the file of this patent UNITED STATES PATENTS 2,368,532 Fearon Jan. 30, 1945 2,488,948 Veazie Nov. 2 2, 1949 2,659,015 Lee Nov. 10*, 1953 2,659,016 Quittner Nov. 10; 1953 

1. AN X-RAY DEVICE COMPRISING AN X-RAY TUBE DISPOSED AT A FIRST PREDETERMINED LOCATION AND INCLUDING A FILAMENT CATHODE AND A CONTROL ELECTRODE, A SOURCE OF TWO CONTROL SIGNALS HAVING RELATIVELY DIFFERENT FIRST AND SECOND FREQUENCIES, RESPECTIVELY, DISPOSED AT A SECOND PREDETERMINED LOCATION, SAID FIRST AND SECOND FREQUENCY SIGNALS BEING ADAPTED FOR THE CONTROL, RESPECTIVELY, OF SAID CONTROL ELECTRODE AND SAID CATHODE, CIRCUIT CONNECTION MEANS TO COUPLE SAID SOURCE TO SAID CONTROL ELECTRODE AND SAID FILAMENT CATHODE COMPRISING A PAIR OF CONDUCTORS HAVING AN INPUT MEANS COUPLED TO SAID SOURCE AND OUTPUT MEANS, FIRST AND SECOND FREQUENCY RESPONSIVE MEANS DISPOSED AT SAID FIRST LOCATION AND COUPLED TO SAID OUTPUT MEANS, SAID FIRST FREQUENCY RESPONSIVE MEANS BEING RESPONSIVE TO A SIGNAL OF SAID SOURCE HAVING SAID FIRST FREQUENCY TO PROVIDE A FIRST OUTPUT SIGNAL TO CONTROL SAID CONTROL ELECTRODE, AND SAID SECOND FREQUENCY RESPONSIVE MEANS BEING RESPONSIVE TO A SIGNAL OF SAID SOURCE HAVING SAID SECOND FREQUENCY TO PROVIDE A SECOND OUTPUT SIGNAL TO CONTROL SAID FILAMENT CATHODE. 